Untitled

clear; clc; close all;

A = imread('peppers.png');

B = rgb2gray(A);

imshow(B)

for j = 1:size(B,1)

Cshift(j,:) = fftshift(fft(B(j,:)));

C(j,:) = fft(B(j,:));

end

imagesc(log(abs(Cshift)))

for j=1:size(C,2)

% Compute column-wise FFT

D(:,j) = fft(C(:,j));

end

imagesc(fftshift(log(abs(D))))

D = fft2(B); % Much more efficient to use fft2

imagesc(fftshift(log(abs(D))))

Image Compression and reconstruction using FFT2

Bt = fft2(B); %2-D fft

Btsort = sort(abs(Bt(:))); %sort by magnitude

for keep = [.1 .05 .01 .002] %percentage of the fft2 matrix to keep

thresh = Btsort(floor((1-keep)*length(Btsort)));

ind = abs(Bt) > thresh;

Atlow = Bt.*ind;

Alow = uint8(ifft2(Atlow));

figure;

imshow(Alow)

title("Reconstructed from " + keep*100 + "% of the original data")

end